8.3. Investigation of the effect of on-site exposure measurements on the risk perception and the credibility of and the confidence in state authorities and grid operators

8.3.a Review of presentation formats for measuremmeasurementent results of low-frequency fields and their importance for risk communication

Project management: Karlsruhe Institute of Technology
Start: 1 December 2018
End: 31 October 2019

Background

Because of the invisibility of electric and magnetic fields from high-voltage power lines, laypersons have to rely on the statements and calculations of experts or on measurements to assess the level of exposure in everyday life. The exposure can be determined with the help of special measuring devices. According to reports from practice, the communication of measurement results has a positive effect on communication processes. Measuring the strength of the field on site therefore seems to have advantages over communicating field strengths based on calculations. However, it is unclear how exactly such measurements and measurement results should be communicated.

Objective

The aim of this project was to empirically investigate what effects different communicative representations of field strengths measurements occurring in the vicinity of high-voltage power lines have on recipients. The following questions were examined in the project:

Question A: Which presentation formats should be used for the on-site measurement and the communication of the measurement results?

After extensive research into the possibilities of presenting measurement results, the following presentation formats were included in the investigation:

1. an (explanatory) video
2. a numerical infographic (bar graph) with supplementary text
3. an explanatory graphic with image and text elements

Question B: What comparisons should be made with other relevant values?

In order to enable citizens to classify the measured value, it must be placed in relation to other variables. In principle, there are three ways to do this:

1. Ratio of the measured value to the limit value
2. Ratio of the (extrapolated) value at maximum system utilisation to the limit value and the measured value
3. Ratio of the measured value to typical values of household appliances (here a hoover was chosen as a specific object of comparison).

Implementation and results

At first a video of an on-site measurement of the magnetic field strength was recorded. This video was shown to test subjects on a computer. The test subjects were then shown information in different presentation formats.

Results for question A (presentation formats)

The test subjects’ ratings of information clarity, usefulness of information, credibility, and complexity of information did not differ significantly from each other. This means that, for these criteria, it basically made no difference in which presentation format the test subjects had received the information. On a descriptive-statistical level, video performed better than the other two presentation formats.

Subjects who had seen the video remembered fewer details than those who had seen one of the graphics. The difference from the explanatory graphic was significant.

The presentation formats differed in their effect on the risk perception of the test subjects: The risk perception in the video group and in the explanatory graphic group decreased but remained about the same in the group that received the numerical infographic. These differences were statistically significant.

Results of Question B (comparison)

The test subjects of all groups rated the three comparisons in terms of

• a) their understandability
• b) their usefulness
• c) how informative they found them
• d) their comprehensibility

A consistent picture emerges across all points:

First, all comparisons were rated rather positively; a classification was thus welcomed by the respondents. Second, the classification of the measured value compared with the limit value as well as the inclusion of the value at maximum system utilisation were assessed positively. The comparison with a household appliance was consistently rated worse on dimensions a) to d); these differences were mostly significant.

Irrespective of the question of the form of presentation or the question of a suitable comparative variable, the communication of the measured value led to a significant overall reduction in the risk perception of the test subjects. Conclusively, it can be said that the project, which had a fairly large random sample of 274 subjects, provided initial findings on how the communication of on-site measurements can be sensibly designed. The results should be interpreted against the background that the test subjects were not actual residents of areas with high-voltage power lines. They only had to imagine that they lived near such a line and that the measurements were communicated to them in this situation. This limitation will be taken up and addressed in follow-up project 8.3.b.

The final report of the project is available in DORIS, the online repository of the BfS.

8.3.b Investigation of the effect of on-site exposure measurements on risk perception as well as the credibility of and trust in state authorities and grid operators

The result developed in the research project “Review of presentation formats for measurement results and measurement uncertainties of high and low-frequency fields and their importance for risk communication” will be verified by measurements on site. In addition, contact will be made with the contractors of the research project “Assessment of exposure to magnetic fields of the general population” (Project 7.2 of the research programme) in order to be able to support some measurements. Various actors are supported socially and scientifically in their on-site measurements.

Residents will be asked to answer the following questions: What are the expectations of on-site measurements? How understandable are the measurement results? How well can the results be classified compared with other field sources? Which factors increase credibility and trust – and which weaken them? Are on-site measurements accepted differently by different actors (e.g. grid operators, state authorities) and perceived as helpful? These questions will be used to review the current strategy for informing the population.